There has been known an electronic control unit having covers that are disposed on the two respective sides of a substrate so as to configure a casing accommodating the substrate in order to protect the substrate from dust, water, and the like. For example, JP2013-165107A discloses an electronic control unit, in which covers are disposed on the two sides of a substrate and fixed to each other by snap fitting.
In the electronic control unit of JP2013-165107A, a first cover is disposed on one side of the substrate and has claw parts on its sidewall, and a second cover is disposed on the other side of the substrate and has through-holes on its sidewall. Each claw part of the first cover is fitted in each through-hole of the second cover, thereby the two covers are fixed to each other.
However, casting of the cover having the through-holes as disclosed in JP2013-165107A requires a movable mold that moves in a direction perpendicular to a mold opening direction in addition to a movable mold that moves in the mold opening direction, leading to a complicated structure of the overall mold. Although drilling may be performed after casting without forming the through-holes during the casting, this inevitably requires a step of removing burrs that occur during the drilling, leading to an increased number of steps.